Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$123.94	13.600%	$140.7958	$140.80	$140.80	$140.80
Purchase #2	$104.72	6.232%	$111.2462	$111.25	$111.25	$111.20
Purchase #3	$99.70	11.715%	$111.3799	$111.38	$111.40	$111.40
Purchase #4	$138.45	4.760%	$145.0402	$145.04	$145.05	$145.00
Purchase #5	$235.63	6.823%	$251.707	$251.71	$251.70	$251.70
Purchase #6	$193.37	10.741%	$214.1399	$214.14	$214.15	$214.10
Purchase #7	$198.65	6.410%	$211.3835	$211.38	$211.40	$211.40
7 purchase totals =	$1,094.46		$1,185.6925	$1,185.70	$1,185.75	$1,185.60